Are you getting connected to Wi-Fi but it’s just showing no connection or the connection is not working.

If so, that would imply your SSID and password are correctly set up at least.

Are the devices getting IP addresses? Can the devices ping the gateway if they are? Are they able to look up DNS?

Ask your college IT department or whoever is responsible for the network in the dorms.

It is possible and even likely that they have a MAC limit set on the port as well and if you exceed that the port can be disabled automatically.

A) I can guarantee you wasted money CAT8 cable for one.

B) You can’t split ethernet like you can a coax TV cable for example or even a phone line. You would need a splitter on both sides that would limit both connections to 100 megabits per second and you would still need an extra port on the the router or switch.

What you need is a network switch. It would plug into an available port on the router, and more devices can plug into it.